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Byoung Ryong Jeong and Chi Won Lee

This study was carried out to determine the interaction among NH4+, NO3-, and Cl- ion uptake and to find the causes of NH4+ -related toxicity symptoms in plants fed with NH4+ as a sole nitrogen source. Seedling plants established in peat-lite and rockwool media were fed with nutrient solutions containing either NH4+ or NO3- or both NH4+ plus NO3- with or without Cl-. Plants grown with NH4+ + Cl- contained the highest levels of Cl-. Plants fed with NO3- + Cl- also showed high levels of Cl- in the tissue. The growth and tissue Cl- contents of plants fed with NH4+ were not affected by changes in Cl- concentration in the nutrient solution. Plants fed with NH4+ that was ion-balanced by high levels of SO42- plus low or no Cl- still developed the NH4+ -related toxicity symptoms. This indicates that NH4+ -related toxicity symptoms occur independently of Cl-. It was also shown that the activity of Cl-, a counterion for NH4+ uptake, was suppressed by NO3-.

Byoung Ryong Jeong and Chi Won Lee

Ageratum and salvia were grown in hydroponic solutions containing either NH4+, NO3-, or both NH4+ and NO3- with or without Cl- to study changes in solution pH and ion uptake rate. pH of both NH4+ and NH4+ + NO3- solutions was steadily decreased as time passed. A drop in pH front 6.50 to 3.57 within 3 days was recorded with NH4+. The pH changes were also affected by the presence of Cl-. The NO3- treatment maintained its initial solution pH over time regardless of the presence of Cl-. pH change by ageratum was greater than that by salvia, especially when plants were in NH4+ + NO3- solution. N uptake was maximum in NH4+ + NO3- solution with Cl-. Uptake of NO3- was suppressed by NH4+, but NH4+ uptake was not affected by NO3-. NH4+ and NO3- counteracted each other in influencing the Cl- uptake. Uptake of other ion was also affected by plant species as well as N source and Cl-. In ageratum transpiration rate was lowered by Cl- in both NH4+ and NO3- treatments.

Byoung Ryong Jeong, Chi Won Lee and Larry S. Daley

A non-destructive in vivo spectroscopic method for leaf chlorophyll (Chl) measurement was developed. Spectroscopic analyses of intact leaves of ageratum, petunia and salvia showed strong correlations between leaf light absorption at 723 nm and Chl-a contents. NH4+ increased Chl contents in both ageratum and petunia whereas NO3- increased Chl contents in salvia. Plants fed with NH4+ + NO3- also contained higher Chl. Chl-a/-b ratio in salvia was lowered by NO3-. Ageratum, petunia and salvia grown with either NH4+, NO3-, or NH4+ + NO3- were also examined for their light absorption characteristics. Light absorption at 705 nm by ageratum and petunia leaves was increased by NH4+ treatment. NH4+ is believed to have changed the structure of photosystem I in both ageratum and petunia but not in salvia. This result explain reasons for salvia's sensitivity to NH4+ fed as a sole N source.

Chi Won Lee, Gye-Soon Jeong and Byoung-Ryong Jeong

Toxicity symptom of micronutrients copper, magnesium and zinc were investigated for geranium, marigold, vinca and zinnia. Plants were grown in peat-lite mix in 11 cm plastic pots and watered with nutrient solutions containing 0.05, 0.5, 1, 5, 10 mM concentrations of Cu2+, Mg2+ and Zn2+. In most species, the concentrations of these micronutrients higher than 5 mM greatly reduced plant growth and induced stem and foliar toxicity symptoms. Toxic levels of Cu2+ and Zn2+ reduced plant and leaf sizes without producing leaf spots in all species tested. Toxicity symptom of Mn2+ were characterized by numerous chlorotic or brown leaf spots. Visual leaf toxicity symptoms of these 3 micronutrients in each species are illustrated.

Byoung Ryong Jeong, Chi Won Lee and Larry S. Daley

A non-destructive in vivo spectroscopic method for leaf chlorophyll (Chl) measurement was developed. Spectroscopic analyses of intact leaves of ageratum, petunia and salvia showed strong correlations between leaf light absorption at 723 nm and Chl-a contents. NH4+ increased Chl contents in both ageratum and petunia whereas NO3- increased Chl contents in salvia. Plants fed with NH4+ + NO3- also contained higher Chl. Chl-a/-b ratio in salvia was lowered by NO3-. Ageratum, petunia and salvia grown with either NH4+, NO3-, or NH4+ + NO3- were also examined for their light absorption characteristics. Light absorption at 705 nm by ageratum and petunia leaves was increased by NH4+ treatment. NH4+ is believed to have changed the structure of photosystem I in both ageratum and petunia but not in salvia. This result explain reasons for salvia's sensitivity to NH4+ fed as a sole N source.

Chi Won Lee, Chun-Ho Pak and Harrison G. Hughes

Stevia (Stevia rebaudiana Bert.) leaves produce stevioside and rebaudioside that can be used as a natural source of low-calorie sweetener which is heat-stable. Because of low fertility, this plant is often vegetatively propagated for field production. This study was conducted to optimize tissue culture procedures for propagating selected clones and explore the feasibility of producing the sweetener compounds by callus cultures. Shoot proliferation was best in Murashige and Skoog (MS) medium supplemented with 0.1 mg/l naphthaleneacetic acid (NAA) Plus 10 mg/l kinetin. Kinetin as a cytokinin source was better than benzyladenine (BA) especially when NAA was present. Callus production fronm leaf disc cultures was most prolific when a combination of 0.1 mg/l NAA and 3 mg/l BA was used in MS medium. The relative sweetener contents of callus cultures are currently being-analyzed.

This study was carried out to determine the influences of planting date (June, July) and soil applications of Trichoderma harzianum (strain T-95) and a fungicide containing ethazole + thiophanate (BanrotR) on flower production of standard carnation cvs. Improved White and Tanga. The one-year production data showed that the fungicide treatment increased flower yield by 7.3% (33.5 flowers/m2) and 4.8% (23.3 flowers/m2) in Improved White and Tanga, respectively, for June planting. Improved White produced more flowers and fancy grades when planted in July as compared to June planting. Planting date did not influence either the yield or the flower quality in Tanga. The effectiveness of Trichoderma as a biological control agent on flower yield and quality was not evident. The patterns of weekly flower production for the two cultivars were determined and graphically illustrated.